Insights into the structural design strategies of multi-spot ultrasonic welded joints in thermoplastic composites: A finite element analysis

Ultrasonic welding is a typical spot-welding technique for thermoplastic composites (TPCs) with high weld strength and short welding time. Therefore, the most straightforward way to apply ultrasonic welding to large-scale TPC structures is adopting multi-spot welded configurations fabricated by a sequential welded method. In order to gain an insight into the structural design optimization strategies of multi-spot welded joints, a finite element (FE) model was proposed in this paper to analyse the mechanical behaviour of a single-lap TPC joints assembled by ultrasonic spot welding. The welded areas were simulated by using cohesive zone elements. The presented FE model was firstly validated by a comparative study between the numerical results and the experimental data. On the basis of that, a comprehensive study was conducted on the effects of typical geometrical parameters, i.e. spot diameters and spot spacing, on the overall mechanical behaviour of the multi-spot welded TPC joints. The numerical results provide a potential guidance for the structural design of ultrasonic welded TPC joints in aircraft structures.